Parsing with stringstream

The string as a stream

#include <sstream>

std::string record = "Linh 20 8.5";
std::istringstream in(record);

std::string name;
int age = 0;
double gpa = 0.0;
in >> name >> age >> gpa;    // "Linh", 20, 8.5

istringstream treats a string like std::cin. >> skips whitespace and converts — an age arrives as a real int, not text. Reading past the end leaves variables untouched and fails the stream: check with if (in >> x) or if (!in) after reading.

Line by line: getline

std::string line;
while (std::getline(in, line)) {   // in can be a file stream too (module 13)
    // process one whole line, spaces included
}

getline reads to the newline and strips it. Mixing >> and getline on the same stream needs care (>> leaves the newline behind — in.ignore() clears it) — this mixing is the single most common stream bug; the exercises exercise it deliberately.

The mini-CSV pattern

// line = "pen,2.5,120"
std::istringstream row{line};
std::string name, price_s, qty_s;
std::getline(row, name, ',');          // "pen"
std::getline(row, price_s, ',');       // "2.5"
std::getline(row, qty_s);              // "120"
double price = std::stod(price_s);     // convert text -> double
int qty = std::stoi(qty_s);

std::getline(stream, out, ',') reads up to a delimiter. std::stoi/std::stod convert text to numbers (they throw on garbage — module 14 handles that properly). This pattern is exactly your module 13 file work and the capstone's storage format, in miniature.

Why not hand-rolled index arithmetic?

Because the stream tools express intent ("read a word", "read to comma") while index math expresses mechanics — and mechanics is where off-by-one bugs breed. Use the tools.